Particle accelerators assist in research providing significant fundamental scientific information beyond that currently available. Particle accelerators also have application in medical therapy and nuclear energy. In addition to the Large Hadron Collider (LHC), the Compact Linear Collider (CLIC) has been proposed at CERN (European Organization for Nuclear Research). CLIC uses different technology than the LHC to achieve a higher planned energy of several TeV. Conventional linear accelerators use a radio-frequency (RF) power to accelerate a main beam generated by devices called klystrons. This creates RF waves. However, klystrons use a large amount of power at high frequencies, and a conventional machine would require many of them in order to reach 3 TeV.
Instead, the CLIC proposal includes the use of two-beam acceleration, involving coupled RF cavities that transfer energy from a high-current, low-energy drive beam to a low-current, high energy accelerated beam to be used for colliding beams of positrons and electrons. Thus, the high-intensity, low-energy drive beam runs parallel to the main linear accelerator beams, and power that is built up in the drive beams can then be transferred in quick bursts to the accelerator beams. This is done by decelerating the drive beam in special power extraction structures (PETS) and the generated RF power is then transferred to the main beam. This allows for a simple tunnel layout with both the drive beam and accelerator beam being generated in a central injector complex and being transported along the linac.
It is hoped that such a design will allow acceleration to reach significantly higher energies (3 to 5 TeV) in a shorter length machine than the more conventional acceleration cavities of the International Linear Collider (ILC) design. FIGS. 1 and 2 illustrate aspects of the CLIC design. Additional information regarding CLIC can be found at http://clic-study.web.cern.ch/CLIC-Study/ and http://preprints.cern.ch/yellowrep/2000/2000-008/p1.pdf, the entire contents of both of which are incorporated herein by reference.
Although the proposed CLIC design simplifies the tunnel layout, such high energy can cause damage in the metal cavities surrounding the beams. The proposed design is prone to breakdown for accelerating fields exceeding 100 MV/m, where electrons and atoms are pulled from the surrounding metal cavity as the electric field becomes high, thereby causing degradation to the accelerator components. Further, the CLIC design is very complex and requires a number of complicated components, such as the PETS and additional transfer structures.
Thus, a need exists in the art for particle accelerators that allow accelerator fields to be sustained at high levels without causing breakdown or degradation of the accelerator cavity or surrounding accelerator structure.